Portable receiver



April 12, 1949. R 5 JOHNSON 2,467,314

PORTABLE RECEIVER Filed Oct. 20, 194 4 2 Sheets-Sheet 1 F|G.l v FIG-3 I Cable Cable Inductance.

Mutual Inductance 7 -27 Large In Fig-l ROLAND S. JOHNSON HIS ATTORNEY III inpuf tuning capacity IO To Cathode To Grid Or A. V. C.

l N V E N T O R April 12, 1949. R. s. JOHNSON PORTABLE RECEIVER Filed 061;. 20, 1944 FIG.6

2 Sheets-$heet 2 ROLAND S. JOHNSON JNVENTOR.

HIS AGE/VT Patented Apr. 12, 1949 Roland s. Johnson, Chicago, 111., assignor "to Zenith Radio Corporation, a 'eorpora'tion "of Illinois Application omen-e0, 1944,-Serial No. 559,512 9 Claims. (01. 550- 1 4 This invention relates to radio receivers a'nd particularly to such receivers'provided with a'loop antenna arranged for use when 'inoun'ted on the receiver and in positions remote from the receiver.

In Patent 2,447,576 to Gilbert E. Gustaf's'on, issued August 24, 1948, entitled Portable radio receiver, and assigned to the same assignee "as the present application, there is describeda portable radio receiver having'a dielectric door'w'hich normally covers the control 'pane1 and which can be rotated into a Vertical position abovethe receiver when the receiver is to be put into operation. A loop antenna structure is inovably mounted on the door and in its mounted condition, th loop iselectrically connected to the recelver, preferably by "means of the door hinges. The connections are made through complementary snap fasteners. When it is desired'to employ the antenna in remote relation to the receiver, the antenna is removed from'the door, suction cups are applied to certain of the snap fastener elements on the'antenna structure and a tape comprising spaced conductors is connected toother snap fastener elements on the door'a'nd on the antenna structure to connect'the loop'to the radi receiver.

The present invention as described in this application applies to this particularradio receiver. However, it must be understood that the invention is clearly applicable to any receiverhaving a loop antenna arranged for operation when mounted on and withinthe receiver and when mounted in remote relation to the receiver,- as for example, on a train window.

When such a loop antenna is directly connected to a radio receiver on the one hand, and then is connected to the receiver by means of a relatively long tape, there is introduced into theantenna circuit a substantial inductance in series with the loop and substantial capacity in shunt with the loop terminals. Consequently, if the tuning condenser tuning the loop input circuit tracks'correctly in'one condition, it will not track inf-the other condition.

It is the principal object of this invention to remove or compensate for the change of capacity and inductance of the loop circuit in both conditions whereby the same calibrated condenser may tune the loop circuit to the same frequency anywhere within a. frequency range for a given setting ofsuch condenser in either condition of the loop circuit.

-A further object of the invention is to provide means for connecting directly and remotely with the aid. of a cable an antenna so that the antenna all '2 circuit eifectively has the same inductance and the same capacity in both cases.

The features of the present invention which are 'b'elieved to be novel are set forth with particularity in the appended claims. The present invention itself, both as to its organization and manner of operation, together with further objects and advantages thereof may best be'understood by reference to the following description taken in connection with accompanying drawings in which;

"Figure '1 is an elevation of a particular preferred embodiment ofthe invention;

Figure '2 is a view similar to that of Figure 1 with certain parts arranged differently;

Figure 3 is a diagrammatic circuit representation of certain' parts of the"appar atusillustrated in Figure 1;

Figure 4"is adiag'raminatic circuit representation of ahdther part of the arrangement shown Figure 1; and

Figure 5 shows circuit'dtails of arrangements of Figures 1 a'nd2;

Figure 6 isa face view of the structure shown schematically in Figure 4;

'--Fi"g'ure7 shows a section of another part in the structure of Figure "1;

Figure 8 is an exploded view of certain parts of the structure shown in Figure 2. I

In Figures 1 and 2, radio apparatuslfl, which may, as illustrated, be a portable radio receiver, is-provicied with a door panel ll which normally cove-rsthe controls [2, dial l3 andspeaker opening-grill I4. The door H is pivotally mbuntedadjacent the center of the top of the receiver In by means of longarmed hingeslfi and 16 in -a manner shown and described more fully in "the disclosure of Patent 2,447,576 to Gilbert E. Gustafson, mentioned previously. These long a'rmed'hinges enable the'door II to pass over-the handle H and to move'through-an angle about 180 into a vertieal'position substantiallyin alignment with the rear wall of .the receiver I0.

Upon the inner side of the door I I are located twosnap fastener elements [8 and I9 which are preferably located in horizontal alignment 7 and which are adaptedto engage complementarysnap fastener elements -20 and 2 I on-the antennastructure 22. Below the snap fastener element I 9 two other snap fastener elements-23 and are located onthe door. These snapfastener elements l3, 24 Y are arranged to be engaged respectively by complementary snap fastener-e1ements 25 and 26- located within the confines of door II and has opposite terminals thereof connected to the snap fastener elements l9 and 23.

The antenna structure 22 includes a loop antenna 28 mounted within the walls defining the structure 22. One terminal of the loop antenna 28 is connected to snap fastener element 25, the other being connected to both snap fastener elements 2| and 26 on opposite sides of element 25.

When the antenna structure 22 is mounted on the door H, as illustrated in Fig. 1, the snap fastener elements 23, 2|, 25, and 26 on the antenna structure 22 engage respectively the snap fastener elements I8, l9, 23, and 24 respectively on the door One terminal of the loop 28v is connected through snap fastener elements 23 and 25 to the right-hand hinge I6 as shown in Fig. 1. The other terminal of the loop 28 is connected through snap fastener elements 24 and 26 by means of a relatively long conductor 29 to the other hinge l5, the conductor 29 being securely mounted in close proximity to the loop 28 when it is mounted on the door for a purpose described later. These hinges are connected in the input circuit of the radio receiver as shown in Fig. 5, hinge |5 being connected to the A. V. C. line or cathode of the first discharge device in the receiver as the case may be and hinge It being connected to the grid of the discharge device. When the antenna structure is so mounted on the door [I the condenser 21 is connected to opposite terminals of the loop.

The antenna structure 22 may be removed from the door upon which it is detachably secured by means of the snap fastener elements described previously and it may be mounted in remote relation to the radio receiver. For this purpose suction cups 30 having cooperating snap fastening elements thereon may be detachably secured respectively to the snap fastener elements 29 and 2|, the suction cups being provided with snap fastener elements complementary to the snap fastener elements 20 and 2|. With the aid of the suction cups the antenna structure 22 may be mounted on a flat surface, for example, the window of a train or other vehicle. The antenna structure is detachably connected to the receiver by means of a tape 3| which may be relatively broad and which carries two conductors 32, 33 located adjacent the edges of the tape so as to minimize capacity therebetween. At each end of the tape the conductors are each connected to respective snap fastener elements which are complementary to, and have the same spacing as, the snap fastener elements 23, 24, and 25, 26 respectively. That is, conductor 32 serves to connect snap fastener element 24 to snap fastener element 26 and conductor 33 serves to connect snap fastener element 23 to snap fastener element 25. The Spacing between snap fastener elements 23 and 24, and the spacing between snap fastener elements 25 and 26 is different from the spacing between the snap fastener element I9 and the snap fastener element 23 and is also different from the spacing between the snap fastener element 2| and the snap fastener element 25, so that snap fastener elements 23A, 24A, 25A and 26A of the tape 3| can only be connected to the snap fastener elements 23, 24, and 25, 26 respectively.

When the antenna structure 22 is mounted remotely relative to the receiver, as illustrated in Fig. 2, the upper terminal or snap fastener element I9 is unconnected, the circuit including the condenser 21 is thereby open and the loop 28 is located in remote relation to the conductor 29. Under those circumstances the circuits of the radio apparatus l are properly adjusted so that 4 the loop 28 is desirably resonant at any frequency within the desired band, taking into account the distributed capacity and the inductance of the two conductors 32 and 33 of the cable or tape 3|.

When the cable or tape 3| is removed and suitably stowed away, and the antenna structure 22 is replaced on the door H by means of the described snap fastener elements, so that the condenser I9 is connected in shunt to the terminals of the loop 28, condenser l9 takes the place, at least in part, of the capacity existing between conductors 32 and 33 of the tape 3|. At the same time, mutual inductance exists between the loop 28 and the long conductor 29 in the door I l, and this mutual inductance is made additive to the inductance of loop 28 and of such amount as to take the place, at least in part, of the inductance of conductors 32 and 33 of the tape 3|.

The conductor 29 is arranged within the door I in a fixed position so that the mutual inductance between it and the loop 28 is preferably substantially equal to the inductance of the cable. By accurate adjustment or selection of the capacity of the condenser 21', and by the provision of the mutual inductance between conductor 29 and the loop 28 in the proper sense the loop circuit is tuned to precisely the same frequency whether the loop structure is mounted on the door II as shown in Fig. 1 or whether it is located in remote relation to the door and connected thereto by the tape 3|.

When the loop 28 is connected through the transmission line or cable 3| to the input terminals formed by hinges |5, It as shown in Fig. 2, the cable 3| connected between the terminals 25, 26 of loop 28 on one end and antenna connections 23, 24 on the other end, the input circuit includes the equivalent cable inductance 33 (Fig. 5) in series with the loop 28 and equivalent cable gapacity 34 in shunt with the loop terminals 25,

When the cable 3i is removed and the loop structure 22 is snapped on the lid ll of the receiver Ill by the snap fasteners previously described as shown in Fig. 1, the cable inductance 33 and cable capacity 34 no longer appear between the loop 28 and the radio apparatus, and if no provision is made to replace such capacity and inductance the first tuned circuit, including tuning condenser 36 (Fig. 5) in the radio apparatus l0, would be improperly tuned to the frequency to which it was tuned when the cable 3| Was connected as shown in Fig. 2. This provision is made by automatically connecting condenser 21 and the equivalent inductance resulting from the mutual inductance between loop 28 and conductor 29 in the antenna input circuit, this mutual inductance being reproducible and accurately determined by the position of the snap fasteners I8. I9. 23 and 24 when the antenna structure 22 is mounted as shown in Fig. 1 but being relatively small when the antenna structure 22 is removed a slight distance from the vicinity of the receiver It). The condenser 21 has a magnitude substantially equal to the equivalent cable capacity represented by condenser 34, and the magnitude of the effective inductance resulting from the mutual inductance between loop 28 and conductor 29 in Fig. 1 is substantially equal to the magnitude of equivalent cable inductance 33.

Therefore, when the loop 28 is remote from the receiver l0 and the cable 3| is inserted in the circuit as shown in Fig. 2, the total circuit inductance and capacitance is the same as when the cable is removed from the circuit and the loop is mounted in predetermined position on lid in as shown in Fig. 1. 7

While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

I claim:

1. The combination with radio apparatus having opposite terminals of a dielectric door adapted to be open for the operation of the apparatus, a loop antenna structure, means including coo-pcrating snap fastener elements on said structure and said door for removably mounting the loop antenna structure on the door, each one of a pair of the snap fastener elements on the door being connected to a respective one of said opposite terminals, each one of a corresponding pair of cooperating snap fastener elements on the structure being connected to a respective one of the opposite terminals of the loop, a condenser carried by the door and having its terminals connected respectively to one of said pair of snap fastener elements on the door and to a third one of the snap fastener elements on the door, a third one of the snap fastener elements on the structure being arranged to cooperate with said third one of the snap fastener elements on the door and being connected to one of said pair of snap fastener elements on the structure, and a two conductor flexible means having at each end a pair of snap fastener elements arranged to cooperate respectively with said pair of snap fastener elements on the door and said pair of snap fastener elements on the structure when the loop structure is operatively connected to the apparatus and situated at a point spaced from the door, said third fastener element on the door and third fastener element on the loop structure connecting said condenser in parallel circuit relationship to said loop when said loop structure is mounted on the door.

2. The combination with radio apparatus having opposite terminals of a dielectric door adapted to be open for the operation of the apparatus, a loop antenna structure, means including snap fastener elements on said structure and said door for removably mounting the loop antenna structure on the door, each one of a pair of the snap fastener elements on the door being connected to a respective one of said opposite terminals, each one of a corresponding cooperating pair of snap fastener elements on the structure being connected to a respective one of the opposite terminals of the loop, a condenser carried by the door and having its terminals connected respectively to one of said pair of snap fastener elements on the door and to a third one of the snap fastener elements on the door, a third one of the snap fastener elements on the structure being arranged to cooperate with said third one of the snap fastener elements on the door and being connected to one of said pair of snap fastener elements on the structure, and a two conductor flexible means having at each end a pair of snap fastener elements arranged to cooperate respectively with said pair of snap fastener elements on the door and said pair of snap fastener elements on the structure When the loop structure is operatively connected to the apparatus and situated at a point spaced from the door, said third fastener element on the door and third fastener element on the loop structure connecting said condenser in parallel circuit relationship to said loop when said loop structure is mounted on the door, the connection from one of the pair of snap fastener elements to the apparatus extending in elongated fashion along part of the door adjacent the normal position of the outer edge of the loop on the door.

3. In a radio receiver having input terminals and a loop antenna structure, the combination of, means for detachably supporting said antenna structure on said receiver in a predetermined po-'- sition with respect thereto, firstmeans for connecting said antenna structure in a circuit with said input terminals only when said supporting means supports said antenna structure in said predetermined position, said antenna structure being arranged to be moved from said predetermined position to a position removed from said receiver, second means for connecting said antenna structure to said input terminals when said antenna structure is at said removed position, said second connecting means having capacity which affects transmission of signals from said antenna structure to said input terminals, and means effective only when said antenna structure is in said predetermined position for adding capacity to said circuit, said added capacity being substantially equal to the capacity of said second connecting means. v

4. The combination with radio apparatus having a pair of terminals of a structure mounted on said apparatus and including a loop antenna having two terminals, three snap fastener elements on said structure, two of said elements being connected to one terminal in said loop antenna, the other of said elements being connected to the other terminal of said loop antenna, said elements being unequally spaced, three snap fastener elements on said apparatus positioned in complementary fastening relation to said elements on said structure, each one of a pair of said elements on said apparatus being connected between which said condenser is connected when.

said structure is mounted on said apparatus, and separate means for connecting said antenna to the terminals of said apparatus, said means com prising conductors having a pair of snap fastener elements on each end arranged to connect respec-- tively with said pair of elements on said apparatus and with the corresponding two elements: on said structure connected respectively to the terminals of said antenna whereby said condenser is connected between said terminals when said structure is mounted on said apparatus and is: out of circuit when said separate means connects said antenna and apparatus.

5. The combination of radio apparatus having a pair of terminals, a loop antenna structure, means for detachably supporting said structure on said apparatus in a predetermined position in respect thereto, means for connecting the loop antenna of said structure in a circuit with said terminals only when said supporting means supports said antenna structure in said predetermined position, said antenna structure being ar-v ranged to be moved from said predetermined position to a position removed from said apparatus, separate means for connecting said antenna in circuit with said terminals when said antenna structure is at said removed position, said separate means having inductance and capacity which aifect transmission of signals between said antenna and said terminals, and means efiective only when said antenna structure is in said predetermined position for adding capacity and inductance to said circuit, said added capacity and inductance being respectively substantially equal to the capacity and inductance of said separate means.

6. The combination of radio apparatus having a pair of terminals, a loop antenna structure, means for detachably supporting said structure on said apparatus in a predetermined position with respect thereto, means for connecting the loop antenna of said structure in a circuit with said terminals only when said supporting means supports said structure in said predetermined position, said structure being arranged to be moved from said predetermined position to a position removed from said apparatus, separate means for connecting said antenna in circuit with said terminals when said structure is at said removed position, said separate means having inductance which affects transmission of signals between said antenna and said terminals, and means eiiective only when said antenna structure is in said predetermined position for adding inductance to said circuit, said added inductance being substantially equal to the inductance of said separate means.

'7. The combination of radio apparatus having a pair of terminals, a loop antenna structure, means for detachably supporting said structure on said apparatus in a predetermined position with respect thereto, means for connecting the antenna of said structure in a circuit with terminals only when said supported means supports said structure in said predetermined position, said structure being arranged to be moved from said predetermined position to a position removed from said apparatus, diiierent means for connecting said antenna in circuit with terminals when said structure is at said removed position, said different means having inductance which affects the transmission of signals between said antenna and said terminals, and means effective only when said antenna structure is in said predetermined position for adding inductance to said circuit, said added inductance being substantially equal to the inductance of said different means, said last means comprising a conductor forming a' portion of said circuit fixed with re spect to said apparatus in a position closely adjacent said predetermined position, the mutual inductance between said conductor and said antenna when in said predetermined position being additive with the inductance of said antenna rid being of an amount substantially equal to the inductance of said different means.

8. The combination with radio apparatus having a pair of terminals and a dielectric door of a loop antenna structure, snap fastener means for detachably supporting said structure in a predetermined position on said door,- said snap ias tener means including snap fastener elements on said door and on said structure connected re spectively with said terminals and with the terminals of the loop antenna of said structure, the elements being separable and said structure thereby being removable from said predetermined position to a position removed from said apparatus, separate means for connecting said elements on said structure and door to connect said antenna and said terminals of said apparatus when said structure is at said removed position, said separate connecting means having capacity which eiiects transmission of signals between said antenna and apparatus, a condenser supported on said door, and means effective only when said antenna structure is in said predetermined position on said door for connecting said condenser between the terminals of said apparatus whereby, when said antenna structure is mounted on said door, said condenser takes the place, at least in part, of the capacity of said separate connecting means and tuning of said antenna in any position is improved.

9. The combination with radio apparatus having a pair of terminals and a dielectric door of a loop antenna structure, snap-fastener means for detachably supporting said structure in a predetermined position on said door, said snap fastener means including complementary snap-fastener elements on said door and on said structure, means for connecting the loop antenna of said structure between said pair of terminals, said last means including a conductor extending from one of said elements on said door past said predetermined position to one of said pair of terminals, said elements being separable and said structure being thereby removable from said predetermined position to a position removed from said conductor, and separate means for connecting said elements on said structure and door to connect said antenna and said terminals when said structure is at such removed position, said separate connecting means having inductance which afiects transmission of signals between said antenna and apparatus, said conductor having such a position with respect to said predetermined position that mutual coupling between said conductor and antenna exists when said structure is in said predetermined position and such mutual coupling is in such sense as to take the place at least in part of the inductance of said separate connecting means whereby tuning of said antenna in any position is improved.

ROLAND S. JOHNSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,292,163 Shea Aug. 4, 1942 2,295,191 Adams Sept. 8, 1942 2,307,805 Schnell Jan. 12, 1943 2,315,315 Cairnes Mar. 30, 1943 2,318,361 Bischofi May 4, 1943 

